Magnetic domain wall propagation in a submicron spin-valve stripe: influence of the pinned layer

The propagation of a domain wall in a submicron ferromagnetic spin-valve stripe is investigated using giant magnetoresistance. A notch in the stripe efficiently traps an injected wall stopping the domain propagation. The authors show that the magnetic field at which the wall is depinned displays a stochastic nature. Moreover, the depinning statistics are significantly different for head to head and tail-to-tail domain walls. This is attributed to the dipolar field generated in the vicinity of the notch by the pinned layer of the spin-valve

South Dakota Corn Performance Test, 1943

The South Dakota Corn Performance Test was designed to supply impartial information concerning hybrids and open-pollinated varieties to the farmers, hybrid-seed-corn dealers and producers, and other persons interested in corn. The plots for this test were in nine areas of eastern South Dakota. There were 362 entries comprising 144 different hybrids and open-pollinated varieties. Two or three adapted open-pollinated varieties were planted in each plot as check varieties. Data are presented on yield, moisture percentage of the grain at harvest, lodging, smut, height, and stand. It should be emphasized that there are many hybrids which have performed well in South Dakota and that the top hybrid in any district for any one year is not necessarily the best one. Statistical measures are included to be used in weighing the advantage or disadvantage of purchasing a given hybrid. Long-time averages are the best indication of the performance of a hybrid. Used with discretion, these data will provide readers with valuable information on the production, sale, and purchase of hybrid corn

The 1942 South Dakota Hybrid Corn Yield Test

Until recently replacement of open-pollinated corn varieties by hybrids has not been as rapid in South Dakota as in states farther east. This reluctance to change has been due primarily to the difficulty of ascertaining the hybrids which will produce the largest average yield under the extremely variable climatic conditions prevalent in the corn growing area of South Dakota. It has been the purpose of these tests to supply information to the purchaser of hybrid corn seed which will enable him to choose adapted high yielding hybrids for his area, and also to provide the producer of hybrid strains with the data necessary to the development of better combinations. As a result of the collection of such data by this and other means the hybrid corn acreage in South Dakota is increasing rapidly

360 degree domain wall generation in the soft layer of magnetic tunnel junctions

High spatial resolution X-ray photo-emission electron microscopy technique has been used to study the influence of the dipolar coupling taking place between the NiFe and the Co ferromagnetic electrodes of micron sized, elliptical shaped magnetic tunnel junctions. The chemical selectivity of this technique allows to observe independently the magnetic domain structure in each ferromagnetic electrode. The combination of this powerful imaging technique with micromagnetic simulations allows to evidence that a 360 degree domain wall can be stabilized in the NiFe soft layer. In this letter, we discuss the origin and the formation conditions of those 360 degree domain walls evidenced experimentally and numerically

Indirect localization of a magnetic domain wall mediated by quasi walls

International audienceThe manipulation of magnetic domain walls in thin films and nanostructures opens new opportunities for fundamental and applied research. But controlling reliably the position of a moving domain wall still remains challenging. So far, most of the studies aimed at understanding the physics of pinning and depinning processes in the magnetic layer in which the wall moves (active layer). In these studies, the role of other magnetic layers in the stack has been often ignored. Here, we report an indirect localization process of 180° domain walls that occurs in magnetic tunnel junctions, commonly used in spintronics. Combining Scanning Transmission X-Ray Microscopy and micromagnetic simulations, magnetic configurations in both layers are resolved. When nucleating a 180° domain wall in the active layer, a quasi wall is created in the reference layer, atop the wall. The wall and its quasi wall must then be moved or positioned together, as a unique object. As a mutual effect, a localized change of the magnetic properties in the reference layer induces a localized quasi wall in the active layer. The two types of quasi walls are shown to be responsible for an indirect localization process of the 180° domain wall in the active layer

Very low 1/f noise at room temperature in fully epitaxial Fe/MgO/Fe magnetic tunnel junctions

We report on room temperature 1/f noise in fully epitaxial Fe(45nm)/MgO(2.6nm)/Fe(10nm) magnetic tunnel junctions (MTJs) with and without carbon doping of the Fe/MgO bottom interface. We have found that the normalized noise (Hooge factor) asymmetry between parallel and antiparallel states may strongly depend on the applied bias and its polarity. Both types of MTJs exhibit record low Hooge factors being at least one order of magnitude smaller than previously reported.Comment: 9 pages, 3 figure

Artificial Kagome Arrays of Nanomagnets: A Frozen Dipolar Spin Ice

Magnetic frustration effects in artificial kagome arrays of nanomagnets are investigated using x-ray photoemission electron microscopy and Monte Carlo simulations. Spin configurations of demagnetized networks reveal unambiguous signatures of long range, dipolar interaction between the nanomagnets. As soon as the system enters the spin ice manifold, the kagome dipolar spin ice model captures the observed physics, while the short range kagome spin ice model fails.Comment: 4 pages, 4 figures, 1 tabl

Phase transition in ultrathin magnetic films with long-range interactions: Monte Carlo simulation of the anisotropic Heisenberg model

Ultrathin magnetic films can be modeled as an anisotropic Heisenberg model with long-range dipolar interactions. It is believed that the phase diagram presents three phases: An ordered ferromagnetic phase I, a phase characterized by a change from out-of-plane to in-plane in the magnetization II, and a high-temperature paramagnetic phase III. It is claimed that the border lines from phase I to III and II to III are of second order and from I to II is first order. In the present work we have performed a very careful Monte Carlo simulation of the model. Our results strongly support that the line separating phases II and III is of the BKT type.Comment: 7 page